Bleaching compositions

ABSTRACT

BLEACHING COMPOSITIONS, USEFUL FOR BLEACHING TEXTILE FIBERS, WHICH ARE AN ALKALINE AQUEOUS SOLUTION CONTAINING A PEROXY COMPOUND, AN ALKALI METAL SILICATE AND A STABILIZER FOR REDUCING THE DECOMPOSITION OF SAID PEROXY COMPOUND AND WHICH IS, FOR EXAMPLE, A COMBINATION OF NITRILOTRIACETIC ACID, 1 - HYDROXY ETHYLIDENE-1, 1-DIPHOSPHONIC ACID, AND A MAGNESIUM OR CALCIUM SALT.

United States Patent 3,795,625 BLEACHING COMPOSITIONS Xavier Kowalski,Creve Coeur, Mo., assignor to Monsanto Company, St. Louis, M0.

N0 Drawing. Filed June 3, 1971, Ser. No. 149,855 The portion of the termof the patent subsequent to Oct. 16, 1990, has been disclaimed Int. Cl.C01b 15/00 U.S. Cl. 252-186 6 Claims ABSTRACT OF THE DISCLOSUREBleaching compositions, useful for bleaching textile fibers, which arean alkaline aqueous solution containing a peroxy compound, an alkalimetal silicate and a stabilizer for reducing the decomposition of saidperoxy compound and which is, for example, a combination ofnitrilotriacetic acid, 1 hydroxy ethylidene-l, l-diphosphonic acid, anda magnesium or calcium salt.

The present invention relates to novel bleaching compositions.Specifically, this invention is concerned with bleaching compositionswhich are aqueous alkaline solutions containing a peroxy compound, analkali metal silicate and a novel combination which functions as astabilizing agent for the reduction of the decomposition of the peroxycompound and prevention of silicate deposition.

Preparing textile materials for bleaching, dyeing and finishinggenerally involves a series of well-known steps. The material is firstsinged to burn off excess fibers, desized to remove any artificialcoating put on the material for processing, rinsed, and then it isscoured. After scouring, the material is again rinsed and then, insuccession, it is bleached, scoured, rinsed, mercerized, rinsed, dyed orprinted, and finished. These steps are more specifically described inChemistry and Chemical Technology of Cotton, Interscience Publishers,Inc., New York, NY. 1955, edited by Kyle Ward, Jr., and which isincorporated herein by reference. A discussion per se of the bleachingstep starts on page 190 of said publication.

In general, bleaching is the fifth major step in the above-describedtextile finishing process. The general purpose of the bleaching step isto oxidize any foreign matter on the textile material in order toprovide a substantially absorbent and white material which is readilyacceptive to dyeing.

The bleaching (oxidative) process is desirable in order to attempt toremove impurities or foreign matter and thus ultimately prepare awhiteness in color product suitable for subsequent dyeing and effectinga uniformity of color thereon. Generally, commercial bleaching(including boiling) processes involve contacting the textile materialwith alkaline aqueous solution (bath) containing a peroxy compound suchas hydrogen peroxide and an alkali metal silicate such as sodiumsilicate.

The use of a stabilizing agent to minimize the decomposition of theperoxy compound is well established in the peroxy bleaching art,because, among other things, the oxygen released by decomposition of theperoxy compound in general has no bleaching action as contrasted withthe normal autodecomposition of the peroxy compound which does functionas a bleaching agent. In fact, the decomposition of the peroxy compoundmay be harmful. For example, cellulosic materials in strongly alkalineperoxy (bleaching) solutions are attacked by the oxygen fromdecomposition with the result of loss of strength by the materials. Ingeneral, stabilizing agents are of various and diverse nature and theability of a material to be an effective stabilizing agent is apparentlyunpredictable. For example, although a few sequestering agents such as3,795,625 Patented Mar. 5, 1974 sodium pyrophosphate can be consideredas stabilizing agents, the majority of sequestering agents are notconsidered to be effective stabilizing agents while such nonsequesteringmaterials as sodium stannate and sodium silicate have been reported asbeing effective stabilizing agents. Therefore, due to theirunpredictability and their diverse nature, the stabilizing agents forperoxy solutions vary in their ability with changes in the prevailingconditions such as pH, temperature conditions and the like of the peroxysolutions. For todays bleaching conditions the stabilizing agent shouldpreferably be effective in alkaline solutions and under relatively hightemperature conditions which are frequently encountered in practice aswell as being compatible with other additives usually present in theperoxy bleaching solutions such as optical whiteners, that is,brighteners or fluorescent white dyes, wetting agents and the like.

Therefore, an object of this invention is to provide an improved methodfor stabilizing aqueous peroxy solutions.

Another object of this invention is to provide a stabilizing agent whichaffects synergism in the reduction of the decomposition of the peroxycompound and also prevents water-insoluble silicate deposition.

Another object of this invention is to provide an improved method forbleaching cellulosic materials using aqueous peroxy solutions havingdissolved therein novel stabilizing agents.

Other objects will become apparent in view of the subsequent detaileddescription and appended claims.

It has been unexpectedly found that the above objects can beaccomplished by including a synergistic stabilizing agent which is acombination of:

(1 nitrilotriacetic acid (NTA) N (CH COOH) 3 and water soluble saltsthereof; (2) l-hydroxy ethylidene-l, l-diphosphonic acid (HEDP) 0 CH3 0Hoi -bi oH HHH and Water soluble salts thereof; and (3) a water solublemagnesium or calcium salt in the aqueous peroxy solution.

It is to be understood in conjunction with the NTA and HEDP acids perse, the water-soluble salts are also included within the scope of thepresent invention. The preferred salts are the sodium salts. Otheralkali metal salts, such as potassium, lithium and the like, as well asmixtures of the alkali metal salts may be used. In addition, anywater-soluble salt, such as the ammonium salt, which exhibit thecharacteristics of the alkali metal salt may be also used to practicethe invention.

The magnesium and calcium salts include, without limitation, magnesiumacetate, magnesium benzoate, magnesium bromate, magnesium bromide,magnesium chlorate, magnesium chloride, magnesium chromate, magnesiumcitrate, magnesium fluosilicate, magnesium formate, magnesium lactate,magnesium nitrate, magnesium nitrite, magnesium hypophosphate, magnesiumselenate, magnesium sulfate, magnesium sulfite, magnesium thiosulfate,calcium butyrate, calcium chlorate, calcium chloride, calciumhypochlorite, calcium chromate, calcium formate, calcium gluconate,calcium lactate, calcium maleate, calcium nitrate, calcium nitrite,calcium propionate, calcium l-quinate, calcium sulfide, calciumdi-thionate, calcium thiosulfate, calcium valerate, and mixtures ofthese salts. The above list is not all inclusive and the magnesium orcalcium salt is anyone which is water-soluble and provides magnesium orcalcium ions in an aqueous system.

It is to be noted that these salts include both inorganic and organicsalts.

It is to be understood that the magnesium or calcium salt can besupplied to the aqueous peroxy solution in the form of the magnesium orcalcium salts of NTA and/or HEDP. In other Words, the novel, stabilizingagent can be in the form of (1) a three component combination of NTA,HEDP, and a magnesium or calcium salt (such as magnesium sulfate), or(2) a two component combination of the magnesium or calcium salts of NTAand HEDP.

It is desirable that the mole ratios of NTAzMg or Ca saltzHEDP be in therange of from about 1:1:1 to about :3:1, preferably from about 2:121 toabout 2:2:1.

It is to be understood that the term textile material as used hereinincludes any natural and/or synthetic fibrous base material such ascotton, nylon, viscose rayon, polyester, e.g., Dacron, hemp, linen,jute, and blends thereof such as, for example, cotton-Dacron, cotton-Dacron-viscose rayon,, cotton-nylon-viscose rayon, cotton-Dacron-nylon,cotton-nylon, and cotton-polyester (all in various weight ratios).

If one so desires to use a surfactant in the peroxy (bleaching)solution, the specific synthetic organic surfactant can be any of a widevariety of surface active agents. Typical surfactants are described inU.S. 2,846,398 and U.S. 3,159,581, both of which are incorporated hereinby reference. Furthermore, other publications which describe surfactantswhich can be used in the present invention processes include Schwartzand Perry, Surface Active Agents, Interscience Publishers, New York(1949) and The Journal of American Oil Chemists Society, vol. 34, No. 4,pages 170-216 (April 1957), both of which publications are incorporatedherein by reference. The amount of surfactant will vary, depending uponvarious process conditions and any amount can be used as long as nosubstantial adverse effect is incurred in the bleaching operation.

Peroxy solutions which are capable of being stabilized in addition tohyrogen peroxide and its addition compounds, such as the peroxide ofsodium and the super oxide of potassium, include urea percompounds,perborates, per sulfates, and the peracids such as persulfuric acid,peracetic acid, peroxy monophosphoric acid and their water-soluble saltcompounds such as sodium, potassium, ammonium and organic amine salts.

Depending upon, inter alia, the particular peroxy-compound used, the pHof the aqueous peroxy solution is usually adjusted with any causticmaterial in order to effect a pH of greater than 7, e.g. inorganicalkali metal basic materials, such as sodium hydroxide, sodiumcarbonate, sodium silicate, diand tri-sodium phosphates and the like,including mixtures of these as Well as the potassium forms of theforegoing materials, to a pH of between about 7.5 and about 12.5.Usually if the pH is higher than about 12.5 rapid bleaching occurs andthe peroxy-compounds rapidly decompose so that it is difficult tocontrol a proper bleaching rate without undue damage to the fibers. AtpH values lower than about 7.0, the rate of bleaching in most cases isslow to the extent of being uneconomical for bleaching. In general, theamounts of caustic used are from about 1% to about 4% by weight based onthe total weight of the alkaline aqueous (peroxy) solution.

The concentration of peroxy solutions can vary depending upon, interalia, the type of peroxy-compound, pH, temperature, type of bleachingdesired and the like, however, normal concentrations, i.e., from about0.01 to about 5% can be used with concentrations from about .2 to about3% being preferred. It is to be understood that the concentration is nota limitation herein and that any concentration can be utilized as longas the desired end result is achieved.

The stabilizing agents of the present invention may be dissolved in theperoxy solution which is ready for use or may be incorporated in aconcentrated peroxy solution, such as a 35% solution of hydrogenperoxide, which is usually further diluted to form the peroxy solutionfor bleaching. In addition, the stabilizing agent can be incorporated indry bleach compositions, such as perborate compositions, by admixingtherewith, and the resulting composition dissolved in the aqueous systemimmediately preceding its end use application. In any event, thestabilizing agent is intended to be used with the peroxy solution at thetime of its use for bleaching purposes.

The concentration of the stabilizing agent of the present invention inthe peroxy solution can vary depending upon, inter alia, concentrationof the peroxy solution, type of peroxy-compound used, pH, temperatureand the like, and usually for normal concentrations of peroxy solutionsand with conventional bleaching methods, the stabilizing agent ispreferably present in concentrations from about 0.001 to about 5% withfrom about 0.1% to about 1% being especially preferred.

The methods for bleaching using the peroxy solutions containing thestabilizing agents of the present invention vary widely, as for example,from using the peroxy solutions at normal temperatures, i.e. from about20 C. to about 35 C. and contacting the textile material by immersionfor periods of time of several hours, i.e., from about 12 to about 36hours, to using the peroxy solutions at temperatures from about 70 C. toabout C. for periods of time from about 30 minutes to about 6-8 hours,as well as continuous bleaching methods which entail the use of theperoxy solutions at normal temperatures, i.e., about 25 C. andcontacting the textile material by saturation, removing the excessmoisture and exposing the textile material to saturated steam attemperatures from about 100 C. to about C. for periods of time from afew seconds (about 20) to about 1 hour and even longer in some cases.U.S. Pats. 2,839,353, 2,960,383, and 2,983,568 are illustrative of beingrepresentative of continuous peroxy bleaching methods.

Additional publications which relate to peroxy bleaching and/orbleaching of textile materials include, without limitation, U.S.2,493,740; U.S. 2,515,532; U.S. 2,524,- 113; U.S. 2,602,723; U.S.2,686,104; U.S. 2,718,528; U.S. 2,740,689; U.S. 2,803,517; U.S.2,820,690, U.S. 2,839,353; U.S. 2,858,184; U.S. 2,868,615; U.S. 2,893,-814; U.S. 2,893,819; U.S. 2,917,528; U.S. 2,927,082; U.S. 2,927,840;U.S. 2,950,175; U.S. 2,960,383; U.S. 2,970,- 882; U.S. 2,983,568; U.S.2,991,168; U.S. 3,003,910; U.S. 3,043,645; U.S. 3,053,634; U.S.3,089,753; U.S. 3,122,- 417; U.S. 3,156,654; U.S. 3,211,658; U.S.3,234,140; U.S. 3,243,378; U.S. 3,278,445; U.S. 3,383,174; Belgium 661,-582; British 793,733; British 852,102; British 866,764; French1,420,462; French 1,999,350; German 1,027,174; Japanese 9600 (57);Japanese 238 (58); Netherlands 6,515,967; and Preparation and Bleaching,Textile World Refresher by K. S. Campbell, 1961 Mc'Graw-Hill PublishingCo., New York. All of these publications are to be considered asincorporated herein by reference.

The temperature of the bleaching (peroxy) solution is desirable in therange of from about 72 F. to the boiling point of the bleaching solutionbut temperatures from about -2l0 F. are preferred. It is to beunderstood that higher temperatures, such as 250 F. to 300 F., can beused (with the aid of superatmospheric pressure) where one so desires.

The practice of the invention and the advantages provided thereby arefurther illustrated by the following examples which are not intended tobe limitative:

EXAMPLE I In order to illustrate the stabilizing ability of thestabilizing agents of the present invention, the following test isconducted with the indicated results.

The bleaching solutions shown in Table I are prepared by mixing together900 milliliters of deionized water, 22 grams of hydrogen peroxide (35%aqueous solution), 11

grams of sodium silicate, 5 grams of sodium hydroxide (50% aqueoussolution) and the indicated amount of the stabilizing agent. Ferroussulfate is added to the resulting solution in an amount to provide 2parts per million (p.p.m.) of Fe++ therein.

Each individual bleaching solution is contained in a suitable Pyrexglass beaker which in turn is in a thermostated bath of the Ahibalaboratory dyeing machine. Each bleaching solution is heated to andmaintained at 210 F. for a period of 120 minutes. At the intervals soindicated in Table I, milliliters (1111.) aliquots of solution arewithdrawn by pipette, quenched in 100 ml. of H 0, acidified with 1 ml.concentrated H 50 and the residual H 0 is titrated with 0.1 N KM O Thepercent available oxygen (remaining in the bleaching solution at thatparticular time) is calculated as follows:

Percent available 0 (mls. KM 4) (normality of Km O (0.008) 100 weight oforiginal H O in solution The results of this test are shown in Table I.

TABLE I example, it is believed that the reaction occurs between thepolysilicic acid through the silanol group and a basic metal ion likeFe(OH) as follows:

While the iron in this form might still act as a catalyst in peroxycompound decomposition, it is believed that the presence of Mg++ and/orCa++ in the peroxy/silicate solution leads to the formation of anextensive network of Mg and/or Ca silicates which form a protectivecolloidal coat over the heavy metal-silicic acid complex, and thusimmobilizes the heavy metal as a catalyst.

It is believed that in the case of the present invention stabilizingagent, i.e., the combination of NTA, Mg and/ or Ca salt and HEDP, the Mgand/or Ca silicate complex does the stabilizing of the peroxy compoundrather than NTA and/ or HEDP. Thus, it is believed that HEDP and NTAserve as a carrier for the Mg and/or Ca and when combined as asequestrant for excessive hardness in bleaching solutions to preventinsoluble silicate precipitates which would adversely effect the overalltextile treat- Efiect of stabilizing agents on peroxide bleach stabilityin deionized water in the presence of 2 p.p.m. Fe++, 22

g./l. H202, 11 g./l. sodium silicate 5 g./l. NaOH, 50% pH 11.3 at 210 F.

Stabilizing agent Present No stainvenbilizing HEDP, ATMP, HEDTA 4 NTA,tion, agent 2 g./l. 2 g./l. 2 gjl. 2 g./l. 2 g./l.

Percent available oxygen remaining in bleach solutions after 5 minutes84 85 97 80 83 98 15 minutes 7 52 92 4 35 94 30 minutes 0 1 4 0 0 84 60minutes-.." 0 0 0 0 0 75 120 minutes 0 0 0 0 0 65 1 Low amounts ofsodium silicate and high pH contribute to peroxide instability.

2 Disodium salt of l-hydroxy ethylidene-l,l-diphosphonic acid.

a Tetra sodium salt of amino tri(methy1ene phosphonic acid)40% solids;note U.S. 3,234,140.

4 Hydroxy ethylene diamine tn'sodium acetate, 40% solids; prior art. 5Trisodium salt of nitrilo triacetic acid.

6 86.1% solution of 1 mole NTA/0.47 mole Mg (from MgSO4)/0.3 mole HEDP;

It is to be noted in Table I, that in addition to the present inventionstabilizing agent, other materials are shown for comparative purposes.Table I readily shows that the sodium salts of NTA and HEDP are poorstabilizing agents as compared to the present invention stabilizingagent (shown in Table I) of the combination of NTA, Mg++ and HEDP. ATMPis representative of the prior art-US. 3,234,140.

EXAMPLE II Example I above is repeated in toto with the sole exceptionthat in place of the 2 p.p.m. Fe++ in the bleaching solution, 2 p.p.m.of Cu++ is present. Substantially the same results are obtained as thatshown in Table I.

EXAMPLE III Example I above is repeated in toto with the sole exceptionthat in place of the 2 p.p.m. Fe++ in the bleaching solution, there ispresent in the solution, by addition of a corresponding water-solublesalt, 0.85 p.p.m. Fe+ 0.17 p.p.m. Cu+ 0.40 Zn++ and 0.10 PbSubstantially the same results are obtained as that shown in Table I.

EXAMPLE IV The exact mechanism of how the novel combination of NTA, HEDPand a water-soluble magnesium and/ or calcium salt effectively act as astabilizing agent is not known. Table I shows, however, that NTA per seand HEDP per se are poor stabilizing agents in an aqueous alkalinebleaching solution containing a peroxy compound and an alkali metalsilicate and catalytically-active substances such as iron, copper,manganese which greatly accelerate the decomposition of theperoxy-compound.

It is believed that the addition of a salt of calcium and/or magnesiumto a solution of a soluble silicate results in a formation of aninsoluble metal silicate. For

ing process. Experimentation has shown that this combination of NTA andHEDP is exceptionally unique and results in unexpected results when usedin combination with a Mg and/or Ca salt. The addition of Mg and/or Casalts, without NTA and/or HEDP, stabilizes peroxy bleaching solutions toa minor degree; however, their use is quite limited because they havepoor solubility and promote insoluble silicate precipitates if used inthe absence of HEDP and NTA.

The above beliefs are merely ideas as to how possibly the stabilizingagent of the present invention functions in a peroxy-silicate bleachingsolution. These ideas are not to be considered as limitations in anymanner whatsoever in the present invention.

TABLE II Effect of additives on the formation of Ca and Mg silicateprecipitates in hydrogen peroxide/sodium silicate bleach solutions 1Grams per liter Hours during 40% solution 05- which H202] silicatesolutions NTA-3Na-Hz0 remained free of plus )4 mole precipitatesNTA-3Na-Hz0 Mg/mole N TA HEDP (clear) l 22 g./l. H20: 35%, 22 g./l.sodium silicate, 0.25 p.p.m. Gu 400 p.p.m. as CaCOz from 2 Cazl Mg (fromCaClz and MgSOi).

In order to demonstrate the effect of NTA, HEDP, Ca and Mg alone or incombination regarding silicate precipitation, eleven bleaching solutions(designated solutions 2-12 in Table II) are prepared in the same manneras set forth in Example I. Solution N0. 1 is a blank with no additivesand is used as a control. Solutions designated Nos. 6-12 arerepresentative of the present invention.

Table II readily shows that NTA per se and a Mg In conjunction withTable III, it is vividly demonstrated that the stabilizing agents of thepresent invention exhibit an unexpected result and are substantiallybetter than the prior art maerials such as ATlMP. Specifically, it canbe seen that with no stabilizing agent in the bleaching solusalt-l-NTAcombination (representative of the prior art) tion, the fabric had awhiteness number of 66; with ATMP are quite inferior if not completelyinefiective in preventthe value was 87 and with DETPA+CaCl the value ingsilicate precipitation in bleaching solutions as comwas 85 and 86. Butwith the novel stabilizing agents of the pared to the novel combinationof NTA, HEDP and a Mg present invention, the average value was 92, asignificant and/ or Ca salt. 10 difierence and improvement. Thesuperiority of these novel In view of the results set forth in ExamplesI-IV, it is stabilizing agents is thus seen. seen that two conditionsmust be concurrently satisfied in The test swatches bleached with thesolution containing order to obtain effective bleaching with an aqueousalkathe present invention stabilizing agents are cut into one linesolution containing a peroxy compound and an alkali inch strips andmeasured for tensile strength according metal silicate, i.e., (1) theperoxy compound must not be to the ASTM Designation D-39-49, Revised1955 Standsubstantially decomposed over a relatively short period rd G lM thod of Testing Woven F b i A Of time, t0 2 hours and silicates in q fBreaking Strength, 11. Raveled Strip method. No substanlmlstl'emdln1I1S0111ti0I 1 and substanllally P P tial degradation of the fabricoccurred as a result of Q Over a {Clam/e Pgrlod of Both of these condlbleaching with the stabilized peroxy solution, i.e., the {10115 aSansfied by the i l h agent of the Present tensile strengths of thebleached swatches compared very mvemlon but not by the mdlvlfiuaicomponents thereof favorably with unbleached swatches which aresimilarly or by the Mg salt+NTA combmanon tested. Consequently, peroxysolutions stabilized with the LE V stabilizing agents of the presentinvention exhibit the In order to illustrate the bleaching ability of aperoxy i i to.blea.c a i Such as Cotton fabnc solution stabilized withthe present invention stabilizing W1 i lmpamng e P i agents (and priorart materials for comparative purposes), While a peroxy solution inaccordance with this ll'lVCll: the following tests are made with theindicated results set F? contam only P Q an alkah forth in Table ULseveral sets of four X swatches metal silicate and the novel stabilizingagents, it will be of unbleached desized sheeting are prewet withdistilled 3O appreciated that the incorporation in the solution ofaddiwater and each set is placed in a suitable stirrer flask contlonallngl'edlellts Commonly used in p y Solutions, taining l1 liter of ableaching solution of the following Such as inorganic alkali metal basicmaterials, Wetting initial composition: 22 grams of a H 0 solution,agents, Optical Whiteners (brightening agents and fl r 11 grams ofsodium silicate, 5 grams of a 50% NaOH cent dyes) and the like, iscontemplated as being within solution, 0.85 p.p.m. Fe++, 0.17 p.p.m. Cu,0.40 p.p.m. 5 the invention. Zn++, 0.10 p.p.m. Pb and the stabilizingagent as indicated The foregoing examples have been de ribed in this inT9131e The tempfifatlll'e was lhelmostated at ab0llt specification forthe purpose of illustration and not limi- 210 F. At intervals of about15 mlnl1t S, 1 allqllots tation. Many other modifications andramifications will of solllflon are Wlthdrflwn y P P and fesldul 292naturally suggest themselves to those skilled in the art determmed bypermanganate tltratlon descnbed m based on this disclosure. These areintended to be com- Exainple I above' The 910th Swatches are WIthFiTaWPafier prehended as within the scope of this invention. t ifie 5 6v 2323:2 1? l zfi g;azi ifigea fl g ggf l g In view of the aforegoing subjectmatter and particularly the examples, it is to be expressly understoodthat pressed and then reflectance measured vs. the original the novelcombination of NTA HEDP and t unbleached cloth. Averages of fourreadings at different 1 bl 1 i Wa cloth orientations are reported. Thedegree of bleaching so u e magneslilm or 0mm Sa t magnesmrp sulis setforth in terms of fabric whiteness as determined fate) fUIICIIOII S IDtwo different aspects: (1) reduction of by a Gardner Automatic ColorDifference Meter made the fiecomposltlon t eperoxy compound and (2)preby Gardner Laboratory, Inc Bethesda, The fabric ventlon of theprecipitation of Water-insoluble silicates. whiteness numbers shown inTable III are determined Thus thg term Stabilizer as used herein isintended to relative to a standard (MgO filter being equal to 100)encompass both of these p The novelty of this hi h was as lo to perfecthit a i ibl unique combination is predicated upon these two aspects Theresults of this Example V are set forth in Table III. (although theexact physical and/or chemical mechanism Regarding these whitenessnumbers, a difference of one is not known) and as such constitutes asignificant adl) unit is considered significant. vancement in the art.

TABLE III Effect of stabilizing agents on peroxide bleach stability andon bleaching of cotton fabric 1 in deionized water in the presence ofseveral heavy metals 1 and at pH 11.3 3

Stabilizing agent DETPA. DETPA Present invention plus plus None AIMP,CaClz 4 CaClz I (control) 4.2a g./l. 4.23 l. 4.23 gJl. 4.2a g./l. 1.75g./l.

Fabric whiteness number 66 87 86 92 92 Percent available oxygenremaining in bleach solutions after- 5 minutes- 61 89 78 77 98 99 15minutes 51 10 17 88 85 30 minutes 6 1 4 77 65 45 minutes 0 2 0 1 68 5260 minutes 0. 5 0 59 40 l 100% cotton fabric, desized and scoured in atextile mill.

a Low amounts of sodium silicate and high pH contribute to peroxideinstability.

4 Diethylene tnamine pentasodium acetate plus CaCh, 24.85% solids.

B Diethylene triamine pentasodium acetate plus CaClz, 32% solids.

a 36.1% solution of 1 mole NTA/0.47 mole Mg/0.3 mole H DP.

1 This solution is extremely unstable and cannot be heated up to 210 F.These values are obtained after heating to 60 C. This solution is notused for bealching of fabric sample.

What is claimed is:

1. A stabilizing agent for reducing the decomposition of a peroxycompound contained in an aqueous alkaline solution and which consistsessentially of a combination of (a) l-hydroxyethylidene-l,l-diphosphonic acid and water-soluble salts thereof, (b)nitrolotriacetic acid and water-soluble salts thereof and (c) awater-soluble salt selected from the group consisting of (1) magnesiumsalts, (2) calcium salts and (3) mixtures of (I1) and (2), wherein themole ratio of (a) to (b) to (c) is respectively from about 1:1:1 toabout 125:3.

2. The stabilizing agent as set forth in claim 1 wherein thewater-soluble salt of item is a magnesium salt.

3. An aqueous alkaline bleaching solution consisting essentially of aperoxy compound and from about 0.001 to about 5 percent by weight of astabilizing agent for substantially reducing the decomposition of saidperoxy compound, said stabilizing agent consisting essentially of acombination of (a) l-hydroxy ethylidene1,ldiphosphonic acid andwater-soluble salts thereof, (b) nitrolotriacetic acid and water-solublesalts thereof and (c) a water-soluble salt selected from the groupconsisting of (1) magnesium salts, (2) calcium salts and (3) mixtures of(1) and (2), wherein the mole ratio of (a) to (b) to (c) is respectivelyfrom about 1:1:1 to about 1:5:3.

4. The bleaching solution as set forth in claim 3 wherein thewater-soluble salt of item (c) is a magnesium salt.

5. The bleaching solution as set forth in claim 3 wherein the peroxycompound concentration is from about 0.01 to about 5 weight percent,based on the total weight of the solution and the stabilizing agentconcentration is from about 0.001 to about 5 weight percent based on thetotal weight of the solution.

6. The bleaching solution as set forth in claim 5 wherein the magnesiumsalt is magnesium sulfate.

References Cited UNITED STATES PATENTS 3,384,596 5/1968 Moyer 252 X3,579,287 5/ 1971 Rowalski 25299 X 3,122,417 2/ 1964 Blaser et a1. 25299UX 3,558,497 1/197 1 Lawes 25299 3,392,121 7/1968 Gedge 25299 UX MAYERWEINBLATT, Primary Examiner US. Cl. X.R.

